| Summary: | <p>Post-harvest produce is subject to contamination by pathogens, and this is currently controlled in the food industry by intervention treatments, such as sodium hypochlorite or peracetic acid. Ozone may be a better alternative because it eliminates the requirement for chemical transportation and storage, and unlike sodium hypochlorite, it does not form toxic residues. The aim of this project was to determine if ozone could be used as an alternative treatment to effectively control pathogens on post-harvest produce.</p>
<p>It was identified that ozone treatment changed the native microbiota of post-harvest produce, and these changes might impact the ability of pathogens to survive and proliferate. Some members of the microbiota were more susceptible to ozone than others, which could have been due to a variety of factors. One factor which was hypothesised to aid the tolerance of pathogens to ozone treatment (in addition to sodium hypochlorite and peracetic acid) was the tolerance that pathogens may have evolved against hydrogen peroxide, which they would encounter during host defences. Since hydrogen peroxide, ozone, sodium hypochlorite and peracetic acid are all strong oxidants, they could be tolerated by the same mechanisms in bacteria. Work in this study however identified that although there were similarities in the response of bacteria to hydrogen peroxide and treatments used in the food industry, an increased tolerance to hydrogen peroxide did not necessarily make them more tolerant to treatments. Finally, it was identified that gaseous ozone, but not aqueous ozone, could be as effective as sodium hypochlorite and peracetic acid against pathogens on post-harvest produce. Overall, this project demonstrated that gaseous ozone could be a promising alternative to the treatments which are currently being used in the food industry.</p>
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